Bilge keel or the like antirolling device for ships



June 21', 1932.

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E. V. TELFER 1,864,102

BILGE KEEL OR THE LIKE ANTIROLLING DEVICE FOR SHIPS Filed April 11, 1950 2 Sheets-Sheet l WOA/VD' June 21, 1932. E. v. TELFER BILGE KEEL OR THE LIKE ANTIROLLING DEVICE FOR SHIPS Filed April 11. 1930 2 Sheets-Sheet 2 Fzg; 2.

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- /NVENTOR ATTORNEY Patented June 21, 1932 Y .fEDMUND-vreroaf'rnnrna,,or NEWcAsTLE-UiaoN-TYNE,ENGLAND EBILGE AKrnfnftut .THE .LIKE .ANTIROLLING DEVICE FOR `SHIPS Application `1e'd`l1pri1 1p1, 1930, Seral'No. 443,495, and in Great Britain April 16, 1929.

This =invention relates *to anti-'rolling de- 'lvices *for ships; "Elie primaryobjectY of the invention is to provide such a. ldevicewhich in addition to being more effective in 'reducing 'tlie'rolling of.v ships thanlthebil'ge'keels hith- -erto used, simultaneously"presents less resistance 7to 'forward movement yand develops a 'forward reaction assistingthe propulsion of vthe vessel when rolling, pitching or heaving. i Hitherto, lbilge E keels have ybeen made of various lforms andcross-*sections butall have extended lcontinuously over a substantial por- 'tion of the length ofthe vessel'. Their action *.is'i'dentica'l with that liofaerofoils of verylow aspect-ratio, since when'the vessel is moving ahead and simultaneously rolling, pitching iorv'hea-ving, the'resultant flow velocity on to suchkeels is inclinedto their vforward translational-direction atan angle corresponding Vto that ofthe resultant of the vessels forward velocity and the ,transverse velocities .due' to rolling, pitching or heaving. Under such 'flow conditions a transverse force isinduced on thev keels and is at right :angles toa direction subtending an angle with the forward `direction something less'thanhalf that subtended by the resultantV velocity. This transverse Lforce thus has :a forward component, but owing to the verylowl aspect-ratio of the keels-liit'heto used'and their non-'streamline foi-mythe induced transverse force is relatively low as is also its angle of forward inclination, and consequently its forward component is very small compared with the sternward resistance of the keels. To improve these conditions by increasing the depth of such keels, thereby increasing their aspectratio and the forward inclination of the induced transverse force is, moreover generally impracticable.

It has been proposed to lit two or more rows of bilge keel sections with gaps therebetween in staggered relation at each bilge. Such arrangement is incapable of developing a forward component of the forces acting thereon during rolling while the increased wetted surface adds appreciably to the skin friction resistance to forward motion of the vessel.

The present invention consists in an antitice. best shownin Figure 54; Y The preferredform `comprises a Lrounded `nosef, maximum` cross- "100 rolling device for ships comprisingarplura'l-l ity of relatively short bilge keels Ofjsymn'ietrical streamline; form with rounded nose and Vtapering run aft spaced apart at intervals longitudinally on each bilgeo'f the 'ship and structurally connected therewith. Saidr short bilge keels kare preferably made with ftheir maximum cross section at aboutonethirdof ltheir-'length fromv the nose.

The greatly increased aspect-ratio ofsuch w improved leels will stillbe small as compared with that of an eliicient yaero'foil. An irnprovement in this respect is effected by fit- -ting the keels along their outboard/edge with half transverse section, of a shipylittedwith a plurality of short bilge keels according to the invention.

FiguresA 3', 4 `and V5 are' views showing'the form `of one of the short bilge keels,`F igure "3 being `an elevation on the ,plane ofysyinmetry of the keel, which plane isthat of the natural hull stream lines and is thus normalornearly 85 so to the surface ofthe hull of the vessel, Figure 4 a section.V at its base`at.theiskingplat ing of the h u1l,-and Figure 5a Vtransverse [view looking af y Figure 'shows a detail.

Figure 7 is a diagramfillustrating theactionof the bilge'keels made'accordingtothe invention.

The short bilge, keels 1 are fixed to thehull 4in rows, one rowy on each side of theship '95 where'long continuous bilge keels have usually been fitted according to present day prac- The streamline forni of thekeelsis section 4 at or near one-third the length from the nose, and sides 5 with a tapering run aft from the maximum section 4 to the tail 6. In cross-section (Fig. 5) the sides 5 taper from a maximum width at the base 7 of the keel at the hull of the ship to a minimum width at the outboard edge 8. A flow-cap or plate 9 is preferably fitted to the outboard edge of each keel substantially parallel to the base thereof at the hull surface. Structurally, in the form illustrated, the bilge keels are made of steel plates 10, angle-bars 11 which are riveted to the hull of the vessel, and a T-bar forming the flow-cap 9. Transverse diaphragm plates may also be fitted at intervals; one is shown at 2 where the nose plate 3 is welded to the side plates 10, and another at or near the maximum cross section 4. The weld joint of nose plate 3, side 10 and diaphragm yplate 2 is shown in section in Figure 6. l

. In a modification, the rounded nose 3,

' which is the leading edge of the keel, may be arranged in elevation (Fig. 3) to slope aft as well as outwards from the hull, so that no obstruction be offered to submerged seaweed or wreckage flowing past.

To guard against internal corrosion, the

.bilge keels may be filled with pitch or other suitable material.

Such improved keels, due to their streamline form, have a low resistance to motion ahead and induce a high transverse force when the vessel is moving ahead and simultaneously rolling,. pitching or heaving.

Their greater aspect-ratio further increases this transverse force and also its forward inclination, so that the forward component of the force is such that it now exceeds the relatively low sternward resist-ance of the keel and thus acts topropel the vessel. This is diagrammatically illustrated in Figure 6,

wherein, following aerofoil theory, the vector a represents the forward speed of the ship, b the linear speed of rolling, and c the speed yof the water flow relative to the bilge keel be- -forc reaching it. The line l represents the reaction of the water on thebilge keel, and

v.the aspect-ratio of the kee being at right angles to a vector intermediate vbetween a and c depending on the aspect-ratio of the keel, has thus a forward component whose-magnitude is the greater the greater Consequently from the adoption of such improved keels the following advantages will accrue The resistance of the ship to rolling, pitching and/or heaving, (and oscillating mot-ions sgenerally) is greatly increased and consequently the amplitudes of such oscillations are reduced.v In all vessels, but particularly .in passenger vessels, this reduction in oscillating motion adds to the comfort of life on board; in war vessels it results in a steadier gun platform; and in all vessels it reduces the loss in speed otherwise occasioned by such oscillating motion. Owing t0 the transverse force induced on the keels having a forward component, some of the external energy causing the ship to oscillate is made available for the propulsion of the ship. In other words, the keels scull their way through the water and hence deliver a useful thrust, thus further reducing the speed loss previously mentioned.

Finally, 'the greatlyV reduced aggregate length of keels made possible by the present invention results in reduced weight and cost. The wetted surface of the keels is simultaneously greatly reduced and this in combina tion withtheir efficient stream-line form, results in a corresponding reduction in their resistance to motion ahead.

I claim :-v

l. An anti-rolling device for ships comv prising a plurality of .relatively short bilge keels of symmetrical stream-line form with rounded nose and tapering run aft spaced apart at intervals longitudinally on each bilge of the ship, said bilge keels beingpro-,fY

vided with flow-caps at their outboard edges substantially parallel vto the hull surface.

, 2. In a ship, a plurality of relatively short bilge keels of symmetrical stream-linefornr Vof cross sections tapering from a maximum width at their bases at the hull surface to a minimum near their outboard edges, isaid bilge keels being provided with flow-caps at their outboard edges substantially parallelL E. V. TELFER.

with rounded nose and tapering run aft and-Q5 

